CN113820397A

CN113820397A - Dead zone inspection with ultrasonic testing using signal integration

Info

Publication number: CN113820397A
Application number: CN202110619090.2A
Authority: CN
Inventors: S·H·米勒; D·M·盖尔; J·W·亚当斯; M·R·布雷; K·D·戈登; C·加尼尔
Original assignee: Boeing Co
Current assignee: Boeing Co
Priority date: 2020-06-03
Filing date: 2021-06-03
Publication date: 2021-12-21
Also published as: US20210382015A1; EP3919897A1; US11454613B2; JP2021192033A; KR20210150987A

Abstract

The present disclosure relates to dead zone inspection using ultrasonic testing using signal integration. And in particular to an ultrasound inspection system, method and software. In one embodiment, the ultrasound inspection system includes an ultrasound probe that introduces ultrasound waves into the structure from the anterior wall and receives reflected waves to generate a response signal. The system also includes a processor that rectifies the response signal to generate a rectified signal, integrates a portion of the rectified signal within a detection time window to determine an energy sum, and generates an output based on the energy sum. The detection time window is defined as the front wall reflection and at least a portion of the near surface dead zone following the front wall reflection.

Description

Dead zone inspection with ultrasonic testing using signal integration

Technical Field

The present disclosure relates to the field of non-destructive inspection (non-destructive inspection) or evaluation of structures.

Background

Non-destructive inspection (NDI) involves inspecting a structure without damaging, or physically altering the structure in a permanent manner. For example, one particular application of NDI is in the aircraft industry, where damage or defects (flaws) to an aircraft structure are inspected during manufacture of the structure and/or after the structure is put into service. Ultrasonic testing is one type of NDI technique. In the pulse-echo mode of ultrasonic testing, the probe sends ultrasonic waves into the structure and detects reflections or echoes of the ultrasonic waves off reflectors (e.g., front wall, back wall, anomalies or defects within the structure, etc.). The time elapsed at the probe from the transmission of the ultrasound waves to the receipt of the reflection is indicative of the depth of the reflector. A typical probe has a piezoelectric component (i.e., transducer) that acts as a transmitter and receiver. The piezoelectric member oscillates in response to the excitation pulse when functioning as a transmitter that transmits the ultrasonic wave, and oscillates in response to the reflection when functioning as a receiver that generates the response signal. After the initial oscillation, the piezoelectric member will continue to oscillate back for a certain time interval, which is referred to as ringing. The ringing of the piezoelectric member creates a dead zone (dead zone) below the front wall of the structure, referred to herein as a near-surface dead zone. In ultrasonic testing, effective detection of anomalies or defects in the near-surface dead zone below the front wall of the structure remains a problem.

Disclosure of Invention

Improved ultrasonic testing techniques are described herein that enable inspection within a near-surface dead zone. By way of overview, the probe emits ultrasound waves into the structure and captures the reflections to generate a response signal. The response signal from the probe (after rectification) includes pulses representing reflections off the front wall of the structure. A portion of the response signal is integrated over a detection time window encompassing the front wall reflection to measure the energy of the response signal at the detection time window. Reflections off anomalies or defects directly below the front wall may be superimposed on the front wall reflections or may be captured as one or more pulses in the response signal after the front wall reflections. By summing the energies of the response signals within the detection time window, anomalies or defects may be detected in the near-surface dead zone. One technical benefit is that ultrasonic inspection may be improved by detecting anomalies or defects directly below the front wall of the structure that were previously undetectable in ultrasonic inspection.

One embodiment includes an ultrasound inspection system. The ultrasound inspection system includes an ultrasound probe configured to introduce ultrasound waves into the structure from the anterior wall and receive reflected waves to generate a response signal. The ultrasound inspection system also includes a processor configured to rectify the response signal to generate a rectified signal, integrate a portion of the rectified signal within a detection time window to determine an energy sum, and generate an output based on the energy sum. The detection time window is defined as the front wall reflection and at least a portion of the near surface dead zone following the front wall reflection.

In another embodiment, the processor is configured to perform negative half-wave rectification and inversion of the response signal to generate a rectified signal.

In another embodiment, the processor is configured to perform positive half-wave rectification on the response signal to generate a rectified signal.

In another embodiment, the processor is configured to full-wave rectify the response signal to generate a rectified signal.

In another embodiment, the processor is configured to define a null gate (null gate) before the front wall reflection and to null the rectified signal within the null gate.

In another embodiment, the processor is configured to generate C-scan data of the structure based on the energy sum.

In another embodiment, the ultrasound inspection system further comprises a robotic arm configured to move the ultrasound probe over the structure; and a position sensor configured to determine position data of the ultrasound probe.

In another embodiment, the processor is configured to trigger an alert when the sum of energies exceeds a threshold.

In another embodiment, the structure comprises a composite part.

In another embodiment, an opaque layer is disposed on the front wall of the composite part; and providing a detection time window based on the depth of the resin pool below the front wall.

In another embodiment, the structure comprises a part of an aircraft.

Another embodiment includes a method of inspecting a structure. The method comprises the following steps: the method includes introducing ultrasonic waves into the structure from the front wall, receiving reflected waves to generate a response signal, rectifying the response signal to generate a rectified signal, integrating a portion of the rectified signal within a detection time window to determine an energy sum, and generating an output based on the energy sum. The detection time window is defined as the front wall reflection and at least a portion of the near surface dead zone following the front wall reflection.

Another embodiment includes a non-transitory computer readable medium embodying programming instructions executed by a processor that direct the processor to implement a method of inspecting a structure. The method comprises the following steps: the method includes introducing ultrasonic waves into the structure from the front wall, receiving reflected waves to generate a response signal, rectifying the response signal to generate a rectified signal, integrating a portion of the rectified signal within a detection time window to determine an energy sum, and generating an output based on the energy sum. The detection time window is defined as the front wall reflection and at least a portion of the near surface dead zone following the front wall reflection.

The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings.

Drawings

Some embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings. The same reference numbers will be used throughout the drawings to refer to the same or like elements.

FIG. 1 is a block diagram of an ultrasound inspection system in an exemplary embodiment.

Figure 2 is an enlarged view of the ultrasonic probe and the anterior wall of the structure.

Fig. 3 is a graph illustrating a portion of the response signal.

FIG. 4 is a flow chart illustrating a method of inspecting a structure in an illustrative embodiment.

Fig. 5 is a graph showing a response signal in an exemplary embodiment.

Fig. 6 is a graph showing a rectified signal in an exemplary embodiment.

Fig. 7 is a graph showing a rectified signal in an exemplary embodiment.

Fig. 8 is a graph showing a rectified signal in an exemplary embodiment.

Fig. 9 is a graph illustrating a detection time window in an exemplary embodiment.

Fig. 10 is another block diagram of an ultrasound inspection system in an exemplary embodiment.

FIG. 11 is a cross-sectional view of a composite part in an exemplary embodiment.

FIG. 12 is a flow chart illustrating a method of inspecting a structure in an illustrative embodiment.

FIG. 13 illustrates an ultrasonic inspection system positioned adjacent to a composite part in an exemplary embodiment.

Fig. 14 is a graph showing a response signal in an exemplary embodiment.

Fig. 15 is a graph showing a rectified signal in an exemplary embodiment.

Fig. 16 is a graph showing an empty door in an exemplary embodiment.

Fig. 17 is a graph illustrating a detection time window in an exemplary embodiment.

Fig. 18 is a C-scan presentation of C-scan data in an exemplary embodiment.

FIG. 19 is a flow chart illustrating an aircraft manufacturing and service method in an exemplary embodiment.

FIG. 20 is a schematic illustration of an aircraft in an exemplary embodiment.

Detailed Description

The drawings and the following description illustrate specific exemplary embodiments. It will be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles described herein and are included within the intended scope of the claims that follow the description. Moreover, any examples described herein are intended to aid in understanding the principles of the disclosure and are to be construed in a non-limiting sense. As a result, the present disclosure is not limited to the specific embodiments or examples described below, but is limited by the claims and their equivalents.

Fig. 1 is a block diagram of an ultrasound inspection system 100 in an exemplary embodiment. The ultrasound inspection system 100 includes a collection of devices or apparatuses, mechanisms, or subsystems configured to perform Ultrasonic Testing (UT) on a structure or test specimen. The ultrasonic inspection system 100 may be used to inspect any number of structures in various industries where it is desirable to detect flaws or defects in a structure, such as the aircraft, automotive, or construction industries. In this embodiment, the ultrasound inspection system 100 includes the following subsystems: an ultrasound probe 102 and a controller 104. The ultrasound probe 102 (also referred to as an ultrasound sensor) is a device or component that transmits or emits ultrasound waves and captures or receives reflections or echoes. The ultrasound probe 102 may include: a single piezoelectric element (PZT) 110 or transducer acting as both a transmitter and a receiver. The controller 104 comprises circuitry, logic, hardware, devices, etc., that is configured to provide excitation signals (i.e., excitation pulses) to the ultrasound probe 102, process response signals from the ultrasound probe 102, and perform other actions for ultrasound measurements. The controller 104 may be implemented on a hardware platform comprised of analog and/or digital circuits. The controller 104 may be implemented on a processor 105 executing instructions 107 stored in a memory 106 (as shown in fig. 1). The processor 105 includes integrated hardware circuitry configured to execute instructions 107, and the memory 106 is a non-transitory computer-readable storage medium for data, instructions 107, etc. and is accessible by the processor 105. The ultrasound inspection system 100 may include various other components not specifically illustrated in fig. 1. For example, the ultrasound inspection system 100 may include: power supplies, network interfaces, user interfaces, etc.

In this embodiment, the ultrasound inspection system 100 is illustrated as performing an inspection of the structure 120. The term "structure" is not meant to be limiting, as the ultrasonic inspection system 100 may be used to inspect any number of parts or structures having different shapes and sizes, such as machined forgings, castings, or composite plates or parts. This inspection may be performed on newly manufactured structures or existing structures that are inspected for preventive maintenance purposes. Further, the structure 120 may be any number of materials. For example, the structure 120 may be a metallic material (e.g., aluminum), a composite material, and the like.

The structure 120 includes a front wall 122 (also referred to as a front surface or face) and a rear wall 124 (also referred to as a rear surface or face). The ultrasound probe 102 is positioned adjacent the anterior wall 122 so as to introduce ultrasound waves 130 from the anterior wall 122 into the structure 120 in a pulse-echo mode. The ultrasound probe 102 may be in contact with the anterior wall 122 or may be separated from the anterior wall 122 by a delay line. Also, a coupling agent 112 (e.g., water or another fluid) may be disposed between the anterior wall 122 and the ultrasound probe 102. The couplant 112 is a material that facilitates transmission of the ultrasonic waves 130 from the ultrasonic probe 102 into the structure 120. The ultrasound probe 102 also receives reflected waves 132 (also referred to as reflections, echoes, or echoes) as the ultrasound waves 130 reflect off reflectors in the structure 120. The ultrasound probe 102 converts the reflected wave 132 into a response signal 108, which is stored or buffered in the memory 106.

Fig. 2 is an enlarged view of the ultrasonic probe 102 and the front wall 122 of the structure 120. When the ultrasound probe 102 emits ultrasound waves 130 that are introduced into the structure 120, a portion of the ultrasound waves 130 will be reflected by the front wall 122 and captured by the ultrasound probe 102 to generate the response signal 108. Typically, there is a dead zone detection gap 210 below the front wall 122 where an anomaly or defect is traditionally not detectable due to ringing of the ultrasonic probe 102. The depth 212 of the dead band detection gap 210 may vary depending on the frequency of the ultrasonic waves 130, the type of material being inspected, and the like. For example, for a 5MHz signal in the composite, the depth 212 may be less than 0.100 inches below the front wall 122. After ringing of the ultrasound probe 102 (i.e., ringing due to reflections off the front wall 122), the depth below the dead zone detection gap 210 may be examined. Thus, the depth directly below the dead band detection gap 210 is referred to as the nearest inspectable depth 214 behind the front wall 122.

Fig. 3 is a graph 300 illustrating a portion of the response signal 108. Note that the excitation or initial pulse applied to the ultrasound probe 102 is omitted from the graph 300. This portion (e.g., a-scan) of the response signal 108 shows a front wall reflection 302 (also referred to as a front surface reflection), and a time interval after the front wall reflection 302. Front wall reflection 302 represents the reflection of ultrasonic waves 130 off front wall 122 of structure 120 (see FIG. 2). The piezoelectric member 110 in the ultrasound probe 102 oscillates upon receiving the front wall reflection 302 to generate the response signal 108 as illustrated in figure 3 and continues to oscillate back for a certain time interval after receiving the front wall reflection 302 (ringing). This creates a dead zone after the front wall reflection 302, referred to herein as a near-surface dead zone (near-surface dead zone) 304. The near-surface dead zone 304 is the time interval after the reflection (e.g., the front wall reflection 302) during which the ultrasound probe 102 oscillates or vibrates due to the reflection. For example, the near-surface dead zone 304 may be one cycle, two cycles, three cycles, etc. of the response signal 108, depending on the damping characteristics of the ultrasound probe 102. Time 306 after the near-surface dead zone 304 represents the nearest inspectable depth 214 below the anterior wall 122 (see fig. 2).

In the embodiments described herein, the ultrasound inspection system 100 is capable of detecting anomalies or defects in the near-surface dead zone 304. FIG. 4 is a flow chart illustrating a method 400 of inspecting a structure 120 in an illustrative embodiment. The steps of method 400 will be described with reference to ultrasound inspection system 100 of fig. 1, but those skilled in the art will appreciate that the methods described herein may be performed by other systems or devices. The steps of the methods described herein are not all inclusive and may include other steps not shown. The steps of the flow diagrams illustrated herein may also be performed in an alternative order.

First, as shown in FIG. 1, the ultrasound probe 102 is positioned adjacent the anterior wall 122 of the structure 120 and operated in a pulse-echo mode to examine the structure 120 at that location. In the pulse-echo mode, the ultrasound probe 102 transforms the electrical pulses into mechanical vibrations. Accordingly, the controller 104 provides excitation pulses to the ultrasound probe 102 (e.g., by a pulse generator). In response to the excitation pulse, the ultrasound probe 102 emits, transmits, or otherwise introduces ultrasound waves 130 from the anterior wall 122 into the structure 120 (step 402). The ultrasonic waves 130 reflected from the structure 120 return to the ultrasonic probe 102 and are converted into a response signal 108. Accordingly, the ultrasound probe 102 receives or captures one or more reflected waves 132 to generate the response signal 108 (step 404). The chronological recording of the amplitude of the response signal 108 may be graphically imaged as a-scan data, as shown in fig. 3.

The controller 104 receives the response signal 108 from the ultrasound probe 102 and stores or buffers the response signal 108. Fig. 5 is a graph 500 illustrating the response signal 108 in an illustrative embodiment. Graph 500 shows a front wall reflection 302 and a back wall reflection 504, the front wall reflection 302 and the back wall reflection 504 representing reflections of the ultrasonic waves 130 off the front wall 122 and the back wall 124, respectively. In fig. 4, the controller 104 then processes the response signal 108 as follows. The controller 104 rectifies the response signal 108 to generate a rectified signal or a processed signal (step 406). The rectified signal may take either a positive or negative domain as desired. In one embodiment, the controller 104 performs negative half-wave rectification and inversion of the response signal 108 in the positive domain to generate a negative half-wave rectified signal (optional step 420). Fig. 6 is a graph 600 illustrating a rectified signal 602 in an exemplary embodiment. In this embodiment, the response signal 108 is negative half-wave rectified and inverted to generate a rectified signal 602. The rectified signal 602 comprises a series of pulses. The pulse in the rectified signal 602 with the first highest peak 610 represents the front wall reflection 302 and may be referred to as the front wall pulse 606.

In another embodiment, the controller 104 performs positive half-wave rectification on the response signal 108 to generate the rectified signal 602 (optional step 422 of fig. 4). Fig. 7 is a graph 700 showing a rectified signal 602 in an illustrative embodiment. In this embodiment, the response signal 108 is positive half-wave rectified to generate a rectified signal 602. Again, the rectified signal 602 includes a series of pulses, and the pulse with the first highest peak 610 (i.e., the front wall pulse 606) represents the front wall reflection 302.

In another embodiment, the controller 104 performs full-wave rectification on the response signal 108 to generate a rectified signal 602 (optional step 424 of fig. 4). Fig. 8 is a graph 800 illustrating a rectified signal 602 in an exemplary embodiment. In this embodiment, the response signal 108 is full-wave rectified to generate a rectified signal 602. In the full-wave rectified signal 602, the front wall reflection 302 is represented by the following two pulses: the pulse with the first highest peak 610 (i.e., leading pulse 606), and the following pulse 806 in the rectified signal 602.

In fig. 4, the controller 104 integrates a portion of the rectified signal 602 that is within a detection time window (step 408). The detection time window is defined as the front wall reflection 302 and at least a portion of the near surface dead zone 304 following the front wall reflection 302. Fig. 9 is a graph 900 illustrating a detection time window 901 in an illustrative embodiment. Graph 900 illustrates a rectified signal 602 generated by negative half-wave rectifying (and inverting) the response signal 108, but a similar process may be performed on a rectified signal 602 generated by positive half-wave rectifying or full-wave rectifying. Different points in time along the rectified signal 602 correspond to different depths within the structure 120. A detection time window 910 (also referred to as a detection gate) is limited or defined by the front wall 122 and the detection gap 210 below the front wall 122. In one embodiment, the controller 104 defines the detection time window 910 to begin at the front wall reflection 302 (i.e., at the front wall pulse 606). For example, when operating in the positive domain, the detection time window 910 may start at the rising edge 920 of the front wall reflection 302, or where the rising edge 920 of the front wall reflection 302 exceeds a threshold voltage (e.g., 0.4 volts). The detection time window 910 ends at a fixed time after the rising edge 920. Thus, the detection time window 910 exclusively encompasses the front wall reflection 302 and the near surface dead zone 304 following the front wall reflection 302. For example, the detection time window 910 may be set or defined to end one period after the front wall reflection 302, two periods after the front wall reflection 302, three periods after the front wall reflection 302, or some other time. The size of detection time window 910 (in time) may be provided based on the frequency of ultrasonic waves 130, the material used for structure 120, the ring time of ultrasonic probe 102, the estimated depth of an anomaly or defect below front wall 122, and the like. Detection time window 910 is set such that the portion of rectified signal 602 that is being integrated is limited to front wall 122 of structure 120 and at least a portion of detection gap 210 below front wall 122 (e.g., below front wall 122 to the nearest inspectable depth 214), and does not include other anomalies or back wall 124 at depths below detection gap 210.

By integrating in this manner, the controller 104 determines the sum of the energies of the portions of the rectified signal 602 that are within the detection time window 910. This energy sum may be used to indicate an anomaly or defect in the inspection gap 210 below the front wall 122. Reflections of anomalies or defects off the underside of the front wall 122 may be superimposed on the front wall reflection 302, which may result in a front wall pulse 606 having a higher peak value. Reflections off of anomalies or defects below the front wall 122 may additionally or alternatively cause one or more additional pulses after the front wall pulse 606. Accumulating the energy within the detection time window 910 has the following technical benefits: these reflections off of anomalies or defects below the anterior wall 122 are captured in the near-surface dead zone 304 so that they can be detected.

In fig. 4, the controller 104 generates the output 150 based on the energy sum (step 410), which is also illustrated in fig. 1. In one embodiment, the controller 104 compares the energy sum to a threshold and triggers an alert 152 or alarm when the energy sum exceeds the threshold (optional step 426). The alert 152 may include: an audible warning, a visual warning, or another type of warning. In another embodiment, the controller 104 generates the C-scan data 154 for the structure 120 based on the energy sum (optional step 428). C-scan refers to an image generated when data collected from an ultrasound examination is plotted as a plan view of the structure 120. Thus, the C-scan data 154 generated by the controller 104 may include data points on a C-scan image of the structure 120. The ultrasound probe 102 is then moved to another position relative to the anterior wall 122 of the structure 120 (step 412), and the method 400 may be repeated at the new position.

The ultrasound probe 102 may be manually moved by an operator to inspect the structure 120 as described above. In another embodiment, the ultrasound inspection system 100 may be automated to move the ultrasound probe 102 for inspection. Fig. 10 is another block diagram of an ultrasound inspection system 100 in an exemplary embodiment. In this embodiment, the ultrasound inspection system 100 further comprises a positioning system 1002, the positioning system 1002 being configured to move the ultrasound probe 102 to different positions along the anterior wall 122 of the structure 120. In this embodiment, the positioning system 1002 includes a robotic arm 1004 and a position sensor 1006 (or multiple position sensors). The ultrasound probe 102 is mounted or attached to a robotic arm 1004 on an end effector or the like. As the robotic arm 1004 moves or scans the ultrasound probe 102 along the structure 120, data is sent to the controller 104 for processing. Based on commands from the controller 104, the robotic arm 1004 is automatically controlled to move the ultrasound probe 102 adjacent to the structure 120. The robotic arm 1004 typically includes multi-axis movement capabilities and uses software support to generate a three-dimensional profile to be used for measurement and inspection of the structure 120. The position sensor 1006 is configured to determine position data 1010 of the ultrasound probe 102 in a coordinate system (e.g., X, Y and Z in three-dimensional space) of the structure 120. The robotic arm 1004 and the position sensor 1006 may communicate with the controller 104 via a wired connection or a wireless connection.

In operation, the robotic arm 1004 moves the ultrasonic probe 102 to a first position relative to the front wall 122 of the structure 120. At this first location, the ultrasound probe 102 and the controller 104 perform the checks described in method 400 to determine the energy sum of the rectified signal 602 at the first location. For example, when generating C-scan data 154, controller 104 converts the energy sum of the first location into a display value, such as a grayscale or color value. The controller 104 also receives position data 1010 for the first location from the position sensor 1006 and associates the position data 1010 for the first location with the display value. The controller 104 may store this information as C-scan data 154. The mechanical arm 1004 then moves the ultrasonic probe 102 to a second position relative to the front wall 122 of the structure 120. At this second location, the ultrasound probe 102 and the controller 104 perform the checks described in method 400 to determine the energy sum of the rectified signal 602 at the second location. Controller 104 converts the energy sum of the second location into a display value, receives location data 1010 for the second location from location sensor 1006, and associates location data 1010 for the second location with the display value. This process is repeated for a plurality of locations to generate C-scan data 154 for structure 120.

In another embodiment, the ultrasound inspection system 100 may also include a network interface 1020 and/or a user interface 1022. The network interface 1020 is a hardware component configured to communicate with remote devices over a network using a wired or wireless connection. The controller 104 may transmit the C-scan data 154 to a remote device over a network using the network interface 1020. User interface 1022 is a hardware component that interacts with an end user or operator. For example, the user interface 1022 may include: a screen or touch screen (e.g., a Liquid Crystal Display (LCD), a Light Emitting Diode (LED) display, etc.), a keyboard or keypad, a tracking device (e.g., a trackball or touch pad), a speaker, and a microphone. The controller 104 may display the C-scan data 154 to the operator via the user interface 1022.

Fig. 11-18 provide examples of ultrasonic testing in another embodiment. Fig. 11 is a cross-sectional view of a composite part 1100 in an exemplary embodiment, which is an example of the structure 120 discussed above. Composite part 1100 is a laminate structure composed of multiple layers of material (e.g., Carbon Fiber Reinforced Polymer (CFRP)) sandwiched together. The individual fibers within the various layers of the laminate structure may be aligned parallel to one another, but different layers may exhibit different fiber orientations in order to increase the strength of the resulting composite part in different dimensions. The laminate structure also includes a resin (e.g., thermoset or thermoplastic) that cures and hardens the layers of the laminate structure into a composite part 1100. Like structure 120, composite part 1100 includes a front wall 122 and a rear wall 124. In this example, an opaque layer 1102 is applied or disposed on the front wall 122. For example, the opaque layer 1102 may be an opaque primer (primer), paint (paint), coating, surface film, or the like. Opaque layer 1102 may be co-cured with composite part 1100. Fig. 11 also illustrates a resin pool 1104 below the front wall 122 that is not visible in the visual inspection method due to the opaque layer 1102. Resin pool 1104 represents an anomaly or defect below front wall 122 that may negatively impact the integrity of composite part 1100, as it may represent a potential crack initiation site. Resin pool 1104 is illustrated as having a depth 1112 below front wall 122. Because resin pool 1104 is proximate front wall 122, it may be located in near-surface dead zone 304 and undetectable using conventional inspection techniques. However, the resin pool 1104 can be detected using the inspection methods taught herein.

FIG. 12 is a flow chart illustrating a method 1200 of inspecting a structure, such as a composite part 1100, in an illustrative embodiment. However, it should be understood that the method 1200 may be used to inspect other types of structures. Method 1200 may include steps similar to those described above for method 400, and those steps are labeled with the same reference numbers.

First, the ultrasonic probe 102 is positioned adjacent the front wall 122 of the composite part 1100 (see FIG. 13) and operated in a pulse-echo mode to inspect the composite part 1100 at that location. Ultrasonic probe 102 introduces ultrasonic waves 130 into composite part 1100 from anterior wall 122 (see step 402 of FIG. 12). The ultrasonic waves 130 are reflected back to the ultrasonic probe 102 and converted into a response signal 108. Accordingly, the ultrasound probe 102 receives one or more reflected waves 132 to generate the response signal 108 (step 404). The controller 104 receives the response signal 108 from the ultrasound probe 102 and stores or buffers the response signal 108. Fig. 14 is a graph 1400 illustrating the response signal 108 in an illustrative embodiment. Graph 1400 shows a front wall reflection 302 and a back wall reflection 504, which represent reflections of ultrasonic waves 130 off front wall 122 and back wall 124, respectively. Response signal 108 represents the raw A-scan data of composite part 1100 at that location.

In fig. 12, the controller 104 processes the response signal 108 as follows. The controller 104 rectifies the response signal 108 to generate a rectified signal by negative half-wave rectifying and inverting the response signal 108 (step 420). Fig. 15 is a graph 1500 showing a rectified signal 602 in an exemplary embodiment. The rectified signal 602 comprises a series of pulses. The pulse in the rectified signal 602 having the first highest peak 610 (i.e., the front wall pulse 606) represents the front wall reflection 302. Although negative half-wave rectification is used in this embodiment, other types of rectification may be used, as described above.

In fig. 12, the controller 104 defines a null gate before the front wall reflection 302 in the rectified signal 602 (step 1202), and nulls the rectified signal 602 within the null gate (step 1204). Fig. 16 is a graph 1600 showing an empty door 1602 in an illustrative embodiment. The blank gate 1602 is used to "zero-out" a portion of the rectified signal that is within the time interval before the front wall reflection 302. Thus, the blank door 1602 starts at a time before the front wall reflection 302 and ends where the front wall reflection 302 starts. For example, the controller 104 may define the end of the blank gate 1602 as being at the rising edge 920 of the front wall reflection 302 (i.e., at the front wall pulse 606), or where the rising edge 920 of the front wall reflection 302 exceeds a threshold voltage (e.g., 0.4 volts). The controller 104 may also define the beginning of the blank 1602 as the number of samples (e.g., 150 samples) prior to the rising edge 920. The portion of rectified signal 602 within blank gate 1602 is taken to be a baseline voltage (e.g., zero volts) so that any pulse prior to front wall reflection 302 does not falsely trigger as front wall reflection 302 in rectified signal 602.

In fig. 12, the controller 104 defines a detection time window 910 or detection gate (step 1206). Fig. 17 is a graph 1700 showing a detection time window 901 in an exemplary embodiment. As described above, the detection time window 910 is limited or defined to the front wall 122 and the detection gap 210 below the front wall 122. In this embodiment, the controller 104 defines the detection time window 910 to begin at the front wall reflection 302 (i.e., at the front wall pulse 606). For example, the detection time window 910 may begin at the rising edge 920 of the front wall reflection 302, or where the rising edge 920 of the front wall reflection 302 exceeds a threshold voltage (e.g., 0.4 volts). The detection time window 910 ends at a fixed time after the rising edge 920. Thus, the detection time window 910 exclusively encompasses the front wall reflection 302 and the near surface dead zone 304 following the front wall reflection 302. The size of the detection time window 910 in this embodiment may be provided based on the estimated depth 1112 of the resin pool 1104 below the front wall 122. Note that as shown in step 1204, the detection time window 910 may begin before the front wall reflection 302 when the portion of the rectified signal 602 that precedes the front wall reflection 302 is made zero. Regardless of where the detection time window 910 begins, the detection time window 910 ends at or before the nearest inspectable depth 214, such that only the front wall 122 and the detection gap 210 directly below the front wall 122 are considered.

In fig. 12, the controller 104 integrates a portion of the rectified signal 602 that is within the detection time window 910 (step 408). By integrating within the detection time window 910, the controller 104 determines the sum of the energies of the portions of the rectified signal 602 that are within the detection time window 910. The controller 104 then generates C-scan data 154 based on the energy sum (step 428). For example, the controller 104 converts the energy sum at the location into a display value and associates the location data 1010 with the display value. The ultrasonic probe 102 is then moved to another position relative to the front wall 122 of the composite part 1100 (step 412), and the method 1200 is repeated at the new position.

After scanning composite part 1100 or at least a portion of composite part 1100, controller 104 may transmit C-scan data 154 to a remote device via network interface 1020 for display by the remote device (step 414), or may display C-scan data 154 via user interface 1022 (step 414). Fig. 18 is a C-scan presentation (C-scan presentation)1800 of C-scan data 154 in an exemplary embodiment. C-scan presentation 1800 provides a plan view of composite part 1100 via a point cloud. Since the controller 104 integrates a portion of the rectified signal 602 within the detection signal window 910 at various locations along the composite part 1100, the C-scan presentation 1800 indicates an anomaly or defect directly below the front wall 122 within the near-surface dead zone 304. In fig. 18, the darker area illustrates the pool 1104 of resin below the front wall 122. One technical benefit is that an operator can detect where resin pool 1104 is present in composite part 1100 even if resin pool 1104 is not visible due to opaque layer 1102 on front wall 122. Another benefit is that because the resin pool 1104 can be detected, the opaque layer 1102 can be co-cured with the composite part 1100 to save manufacturing time.

Again, although method 1200 is used to describe inspection of composite part 1100, the method may be used to inspect other types of structures. For example, the method 1200 may be used to detect inclusions or voids below the front wall of a metal part.

Embodiments of the present disclosure may be described in the context of aircraft manufacturing and service method 1900 as shown in FIG. 19 and aircraft 2000 as shown in FIG. 20. During pre-production, exemplary method 1900 may include specification and design 1904 of aircraft 2000 and material procurement 1906. During production, component and subassembly manufacturing 1908 and system integration 1910 of aircraft 2000 may occur. Thereafter, the aircraft 2000 may undergo certification and delivery 1912 in order to be placed into service 1914. When used by a customer, the aircraft 2000 is scheduled for routine maintenance and service 1916 (which may also include modification, reconfiguration, refurbishment, and so on).

Each of the processes of method 1900 may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For purposes of this description, a system integrator may include, but is not limited to, any number of aircraft manufacturers and major-system subcontractors; the third party may include, without limitation, any number of vendors, subcontractors, and suppliers; and the operator may be an airline, leasing company, military entity, service organization, and so on.

As shown in fig. 20, an aircraft 200 produced according to exemplary method 1900 may include an airframe 2002 with a plurality of systems 2004 and an interior 2006. Examples of high-level systems 2004 include one or more of a propulsion system 2008, an electrical system 2010, a hydraulic system 2012, and an environmental system 2014. Any number of other systems may be included. Although an aerospace example is shown, the principles described in this specification may be applied to other industries, such as the automotive industry.

During any one or more of these stages of production and service method 1900, the apparatus and methods embodied herein may be employed. For example, components or subassemblies corresponding to production process 1908 may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft 2000 is in service. Also, during

production stages

1908 and 1910, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized, for example, by substantially expediting assembly of aircraft 2000 or reducing the cost of the aircraft. Similarly, when the aircraft 200 is in use, one or more of the apparatus embodiments, the method embodiments, or a combination thereof may be utilized for maintenance and service 1916, for example and without limitation.

Clause 1. an ultrasonic inspection system (100), the ultrasonic inspection system (100) comprising:

an ultrasound probe (102) configured to introduce an ultrasound wave (130) into the structure (120) from the front wall (122) and to receive a reflected wave (132) to generate a response signal (108); and

a processor (105) configured to rectify the response signal to generate a rectified signal (602), integrate a portion of the rectified signal within a detection time window (910) to determine an energy sum, and generate an output (150) based on the energy sum;

wherein the detection time window is defined as a front wall reflection (302) and at least a portion of a near surface dead zone (304) following the front wall reflection.

Clause 2. the ultrasonic inspection system (100) of clause 1, wherein:

the processor is configured to perform negative half-wave rectification and inversion on the response signal to generate the rectified signal.

Clause 3. the ultrasonic inspection system (100) of clause 1 or 2, wherein:

the processor is configured to perform positive half-wave rectification on the response signal to generate the rectified signal.

Clause 4. the ultrasonic inspection system (100) of clause 1, 2, or 3, wherein:

the processor is configured to full-wave rectify the response signal to generate the rectified signal.

Clause 5. the ultrasonic inspection system (100) of any of clauses 1-4, wherein:

the processor is configured to define an empty door (1602) before the front wall reflection and to null the rectified signal within the empty door.

Clause 6. the ultrasonic inspection system (100) of any of clauses 1-5, wherein:

the processor is configured to generate C-scan data (154) of the structure based on the energy sum.

Clause 7. the ultrasound inspection system (100) according to clause 6, the ultrasound inspection system (100) further comprising:

a robotic arm (1004) configured to move the ultrasound probe over the structure; and

a position sensor configured to determine position data of the ultrasound probe.

Clause 8. the ultrasonic inspection system (100) according to any of clauses 1-7, wherein:

the processor is configured to trigger an alert (152) when the energy sum exceeds a threshold.

Clause 9. the ultrasonic inspection system (100) of any of clauses 1-8, wherein:

the structure includes a composite part (1100).

Clause 10. the ultrasonic inspection system (100) of clause 9, wherein:

an opaque layer (1102) is disposed on a front wall of the composite part; and

the detection time window is provided based on a depth (1112) of a resin pool (1104) below the front wall.

Clause 11. the ultrasonic inspection system (100) of any of clauses 1-10, wherein:

the structure comprises a part of an aircraft (2000).

Clause 12. a method (400) of inspecting a structure, the method comprising the steps of:

introducing (402) ultrasound waves into the structure from the front wall;

receiving (404) the reflected wave to generate a response signal;

rectifying (406) the response signal to generate a rectified signal;

integrating (408) a portion of the rectified signal within a detection time window to determine an energy sum; and

generating (410) an output based on the energy sum;

wherein the detection time window is defined as a front wall reflection and at least a portion of a near surface dead zone following the front wall reflection.

Clause 13. the method (400) of clause 12, wherein the step of rectifying the response signal comprises:

-negative half-wave rectifying and inverting (420) the response signal to generate the rectified signal.

Clause 14. the method (400) of clause 12 or 13, wherein generating an output based on the energy sum comprises:

c-scan data for the structure is generated (428) based on the energy sum.

Clause 15. the method (400) of clause 12, 13 or 14, wherein generating an output based on the energy sum comprises:

triggering (426) an alert when the energy sum exceeds a threshold.

Clause 16. the method (400) according to any of clauses 12-15, wherein:

the structure comprises a composite part;

an opaque layer is disposed on the front wall of the composite part; and

the detection time window is provided based on a depth of the resin pool below the front wall.

Clause 17. a non-transitory computer readable medium (106) embodying programmed instructions (107) for execution by a processor (105), wherein the instructions direct the processor to implement a method of inspecting a structure (120), the method comprising the steps of:

introducing ultrasound waves (130) into the structure from the front wall (122);

receiving the reflected wave (132) to generate a response signal (108);

rectifying the response signal to generate a rectified signal (602);

integrating a portion of the rectified signal within a detection time window (910) to determine an energy sum; and

generating an output (150) based on the energy sum;

Clause 18. the computer-readable medium (106) of clause 17, wherein the step of rectifying the response signal comprises:

negative half-wave rectification and inversion of the response signal to generate the rectified signal.

Clause 19. the computer-readable medium (106) of clause 17 or 18, wherein generating an output based on the energy sum comprises:

c-scan data (154) of the structure is generated based on the energy sum.

Clause 20. the computer-readable medium (106) of clause 17, 18, or 19, wherein generating an output based on the energy sum comprises:

triggering an alert (152) when the energy sum exceeds a threshold.

Any of the various elements shown in the figures or described herein may be implemented as hardware, software, firmware, or some combination of these. For example, the elements may be implemented as dedicated hardware. A specific hardware element may be referred to as a "processor," "controller," or some similar terminology. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term "processor" or "controller" should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, Digital Signal Processor (DSP) hardware, network processor, Application Specific Integrated Circuit (ASIC) or other circuitry, Field Programmable Gate Array (FPGA), Read Only Memory (ROM) for storing software, Random Access Memory (RAM), non volatile storage, logic, or some other physical hardware component or module.

Also, the elements may be implemented as instructions executable by a processor or a computer to perform the functions of the elements. Some examples of instructions are software, program code, and firmware. The instructions are operable when executed by the processor to direct the processor to perform the functions of the elements. The instructions may be stored on a storage device readable by a processor. Some examples of storage devices are digital or solid state memory, magnetic storage media such as disks and tapes, hard drives, or optically readable digital data storage media.

Although specific embodiments have been described herein, the scope is not limited to those specific embodiments. But instead the scope is defined by the appended claims and any equivalents thereof.

Claims

1. An ultrasound inspection system (100), the ultrasound inspection system (100) comprising:

an ultrasound probe (102), the ultrasound probe (102) being configured to introduce an ultrasound wave (130) into the structure (120) from the front wall (122) and to receive a reflected wave (132) to generate a response signal (108); and

a processor (105), the processor (105) configured to rectify the response signal to generate a rectified signal (602), integrate a portion of the rectified signal within a detection time window (910) to determine an energy sum, and generate an output (150) based on the energy sum;

2. The ultrasound inspection system (100) of claim 1, wherein:

3. The ultrasound inspection system (100) of claim 1 or 2, wherein:

4. The ultrasound inspection system (100) of claim 1 or 2, wherein:

5. The ultrasound inspection system (100) of claim 1 or 2, wherein:

6. The ultrasound inspection system (100) of claim 1 or 2, wherein:

7. The ultrasound inspection system (100) of claim 6, further comprising:

a robotic arm (1004) configured to move the ultrasound probe over the structure (1004); and

8. The ultrasound inspection system (100) of claim 1 or 2, wherein:

9. The ultrasound inspection system (100) of claim 1 or 2, wherein:

the structure includes a composite part (1100).

10. The ultrasound inspection system (100) of claim 9, wherein:

an opaque layer (1102) is disposed on a front wall of the composite part; and

11. The ultrasound inspection system (100) of claim 1 or 2, wherein:

the structure comprises a part of an aircraft (2000).

12. A method (400) of inspecting a structure, the method (400) comprising the steps of:

introducing (402) ultrasound waves into the structure from the front wall;

receiving (404) the reflected wave to generate a response signal;

rectifying (406) the response signal to generate a rectified signal;

generating (410) an output based on the energy sum;

13. The method (400) of claim 12, wherein rectifying the response signal comprises:

14. The method (400) of claim 12 or 13, wherein generating an output based on the energy sum comprises:

c-scan data for the structure is generated (428) based on the energy sum.

15. The method (400) of claim 12 or 13, wherein generating an output based on the energy sum comprises:

triggering (426) an alert when the energy sum exceeds a threshold.

16. The method (400) of claim 12 or 13, wherein:

the structure comprises a composite part;

an opaque layer is disposed on the front wall of the composite part; and

17. A non-transitory computer readable medium (106) embodying programmed instructions (107) for execution by a processor (105), wherein the instructions direct the processor to implement a method of inspecting a structure (120), the method comprising the steps of:

receiving the reflected wave (132) to generate a response signal (108);

rectifying the response signal to generate a rectified signal (602);

generating an output (150) based on the energy sum;

18. The computer-readable medium (106) of claim 17, wherein rectifying the response signal comprises:

19. The computer-readable medium (106) according to claim 17 or 18, wherein generating an output based on the energy sum comprises:

c-scan data (154) of the structure is generated based on the energy sum.

20. The computer-readable medium (106) according to claim 17 or 18, wherein generating an output based on the energy sum comprises:

triggering an alert (152) when the energy sum exceeds a threshold.